In the systems, that are known from e.g. U.S. Pat. No. 6,315,079, the lifting columns are disposed displaceably on a workshop floor, and over the workshop floor are arranged the cables that are required for electric power supply to the drive and control of the lifting columns, as well as conductors for mutual contact between the controls of the individual lifting columns.
Therein, an energy source such as wall sockets have to be available at the workshop floor. Also, the cables from, to and between the lifting columns are often in the way on the workshop floor, wherein people can trip over them, which can cause a hazardous situation. Further, when the setup or configuration of the individual lifting columns has to be changed, all cabling has to be disconnected, where-after the lifting columns can be displaced to the desired positions thereof, followed by reconnection of all cables for energy supply and for mutual contact.
The couplings can be damaged as a result of frequent disconnection of the cabling for a new setup or because of the danger of someone stumbling over the cables and thereby disconnecting the cables, after which the cables have to be replaced and work on the workshop floor has to be interrupted until new cables are in place. When couplings are damaged or couplings which have merely been pulled out, failure of the system could occur which could then in turn result in a hazardous situation for the users of the system. The position of a lifting column in the known system is, through physical connection thereof with a socket, determined by the identification or address of the socket, rather than the lifting column itself.
Such systems are also known from for example WO 92/19.527, wherein radiographic communication means can be employed. Such communication can remedy some of the drawbacks mentioned above, but the disclosure of this document is restricted to deployment of a single fixed group of columns, and communication can, in use of the system for lifting objects, be useful in said use. However, prior to or in the course of this use, the system requires set-up or re-configuration of the individual lifting columns in the system, as noted above.
Without the sockets of a cable based system, assigning an address or identification to a desired one of the lifting columns is a severe problem, that is according to the disclosure of WO 92/19.527 avoided with a system comprising a group of a fixed number of predetermined lifting columns. However, for many applications more flexibility is desired, for instance when adding or removing lifting columns to or from a subgroup, that is actually used for lifting different objects, such as vehicles of varying size.